This specification relates to data processing and combining components from different sources.
The Internet facilitates the exchange of information between users across the globe. This exchange of information enables distribution of content to a variety of users. In some situations, content from multiple different providers can be integrated into a single electronic document to create a composite document. For example, a portion of the content included in the electronic document may be selected (or specified) by a publisher of the electronic document. A digital component (e.g., a different portion of content) can be provided by a third-party (e.g., an entity that is not a publisher of the electronic document), and integrated into the electronic document with the portion of content selected by the publisher. In some situations, the digital component is selected for integration with the electronic document after a user has already requested presentation of the electronic document. For example, machine executable instructions (e.g., a script) included in the electronic document can be executed by a client device when the electronic document is rendered at the client device, and the instructions can enable (e.g., program) the client device to contact one or more remote servers to obtain one or more digital components that will be integrated into the electronic document, for example at the client device.